Megakaryocytes in a hemorrhagic pleural effusion caused by anticoagulant overdose.

Sudden widespread hemorrhage, including a hemorrhagic pleural effusion, developed in a patient due to an overdose of anticoagulant. The pleural fluid contained megakaryocytes. Necropsy did not reveal myeloid metaplasia or any myeloproliferative disorder. Since megakaryocytes are normally found in pulmonary parenchyma, their presence in the pleural fluid was attributed to the hemorrhagic condition of the lung, which enabled megakaryocyte-containing blood to enter the pleural cavity.